Hello , I am new to the arduino. i have learn about arduino in different magazine . it is very interesting and easy to make project . now i am decided to buy Arduino board . But my Question is , what board i will buy?? i have know c and c++ language(Not expert) and little bit about microprocessor and micro-controller. Please help me.Thank you.

You may want to consider purchasing a kit if you haven't made your purchase yet. I bought mine for $100 shipped from Canada and it was the ARDX Experimenter's Kit ordered from Solarbotics. The decision to go with this kit was directly influenced by this Arduino Starter Rundown article outlining what each kit contained:

http://aaroneiche.com/2009/07/16/arduino-starter-rundown-part-2/

This one was recommended by the author as one of the ones having the most features and one of the better documented. The little handbook you get is complete with a programming and electrical engineering primer to get you oriented with basic electrical components, their functions, and also provides breadboard overlays to guide the very connections you make on your breadboard if you need it. The only page that needs updating is the RGB page where the LEDs don't light up correctly, but by the time you get to that chapter, you should know enough to get that figured out with some research.